As the operating speed of printers which are used in conjunction with computers, word processors, and electronic typewriters, is increased through technological advancement, there is a correspondingly increasing need for providing such printers with large stores of printing ribbon. Such a need is particularly acute in printers which use ribbon of the type which has an ink coating on a thin plastic substrate. In contrast to fabric ribbons which may be reused or reinked, the ink coating on full release film ribbons is consumed by the printing process such that a fresh ribbon portion is required for each impact operation of the printer. Even known partial release film ribbons can accept only two or three printing impacts in a given area.
In commercially available printers of the fully-formed character impact type which produce correspondence-quality results, the largest available ribbon supplies are generally on the order of one million characters. Since such correspondence-quality printers may operate at rates of up to sixty characters per second, the useful life of a one million character ribbon supply, in continuous use, in less than five hours. It is therefore evident that in a business environment such correspondence-quality printers require the ribbon to be replaced at least once each day.
The reason why the capacity of a ribbon store in a conventional printer is so limited is simply a matter of bulk and mass. Since printers generally carry the ribbon store on a moving carriage which also carries the printing element and its associated drive components, engineering compromises have to be negotiated between carriage performance and the capacity of the ribbon store. As is well known, the carriages of printers generally travel along a straight path in the vicinity of a stationary platen which supports the paper to be printed when the printing element is driven to impact upon the paper. For each printing position where a character, symbol, or element of punctuation is to be printed, the carriage is moved quickly to that location such that it registers with the print zone of the carriage, and the carriage is stopped during printing. It is therefore evident that the motion of the carriage is discontinuous requiring a substantial number of starts and stops across each line of printing. It is elemental that the acceleration and deceleration characteristics of a body are functions of the mass of the body and its structural configuration. In essence, an increase in the capacity, and therefore the mass, of the ribbon store is achieved at the expense of carriage performance and printer speed.
It is, therefore, an object of this invention to provide a ribbon store for printers which has greater capacity than conventional ribbon stores.
It is another object of this invention to provide a high capacity ribbon storage arrangement which does not substantially degrade carriage performance.
Conventional ribbon supply arrangements are provided with a ribbon drive which causes the ribbon to be transported from a feed reel, past a ribbon utilization area, to a take-up reel. In such known ribbon supply systems, the ribbon is driven by a drive arrangement which rotates the take-up reel so as to wind the used ribbon thereon. Direct coupling of the drive arrangement to the take-up reel has been preferred because other ribbon guide and drive arrangements would require the ribbon to be gripped on both sides by a capstan and a roller, or two rollers. Such a mechanical engagement with the inked side of the ribbon causes the residual ink to be at least partially removed from the film substrate, resulting in an accumulation of ink particles which, as the carriage is moved discontinuously, are distributed throughout the internal mechanism of the printer thereby increasing the frequency of service calls. In addition, irrespective of whether the ribbon is driven by a combination of rollers, or the take-up reel, a driver, such as a stepper motor, must be incorporated on the carriage, further increasing its mass and degrading its performance.
It is therefore a still further object of this invention to provide a drive arrangement for a ribbon which minimizes dislodgment of ink particles from the ribbon.
It is also an object of this invention to provide a drive arrangement which does not require a ribbon drive motor to be arranged on the carriage of the printer.